1. Field of the Invention
This invention relates to focusing devices adapted to endoscopes and the like and more particularly to a focusing device of a system of detecting focusing displacement by utilizing the displacement in the direction vertical to the optical axis of an image by two light bundles divided except at the time of focusing by dividing by the time or space a part of a light bundle passing through or near a pupil of such optical system as of a microscope.
2. Description of the Prior Art
There is such conventional focusing device of this kind of type as is mentioned, for example, in Japanese Patent Publication No. 13929/1981. However, this is not of an idea of detecting the lateral displacement itself of an image but is of an idea of judging focusing when the light amount observed at one point varies as a result of an image causing lateral displacement and becomes equal to the light amount observed at another conjugate point. Therefore, there have been problems that the information of the entire image can not be effectively used, the sensitivity of focusing is low and a mis-operation is likely to be caused. Also, it is to detect only the peak value the same as in the conventional system of photoelectrically detecting the contrast of an object to be photographed. Therefore, there have been problems that whether focusing is front or rear can not be judged and that the amount of deviation of focusing can not be detected. Further, there has been a problem that, if the light division fluctuates, the light amounts of two images will be different from each other and therefore mis-focusing will be made.